The rho family of small GTP binding proteins can be activated by several extracellular stimuli such as growth factors, hormones and mechanic stress and function as a molecular signaling switch by cycling between an inactive GDP-bound form and an active GTP-bound form to elicit cellular responses. Rho-kinase (ROCK) functions as a key downstream mediator of Rho and exists as two isoforms (ROCK 1 and ROCK 2) that are ubiquitously expressed. ROCKs are serine/threonine kinases that regulate the function of a number of substrates including cytoskeletal proteins such as adducing, moesin, Na+—H+ exchanger 1 (NHE 1), LIM-kinase and vimentin, contractile proteins such as the myosin light chain phosphatase binding subunit (MYPT-1), CPI-17, myosin light chain and calponin, microtubule associated proteins such as Tau and MAP-2, neuronal growth cone associate proteins such as CRMP-2, signaling proteins such as PTEN and transcription factors such as serum response factor (Loirand et al, Circ Res 98:322-334 (2006)). ROCK is also required for cellular transformation induced by RhoA. As a key intermediary of multiple signaling pathways, ROCK regulates a diverse array of cellular phenomena including cytoskeletal rearrangement, actin stress fiber formation, proliferation, chemotaxis, cytokinesis, cytokine and chemokine secretion, endothelial or epithelial cell junction integrity, apoptosis, transcriptional activation and smooth muscle contraction. As a result of these cellular actions, ROCK regulates physiologic processes such as vasoconstriction, bronchoconstriction, tissue remodeling, inflammation, edema, platelet aggregation and proliferative disorders.
One well documented example of ROCK activity is in smooth muscle contraction. In smooth muscle cells ROCK mediates calcium sensitization and smooth muscle contraction. Agonists (noradrenaline, acetylcholine, endothelin, etc.) that bind to G protein coupled receptors produce contraction by increasing both the cytosolic Ca2+ concentration and the Ca2+ sensitivity of the contractile apparatus. The Ca2+-sensitizing effect of smooth muscle constricting agents is ascribed to ROCK-mediated phosphorylation of MYPT-1, the regulatory subunit of myosin light chain phosphatase (MLCP), which inhibits the activity of MLCP resulting in enhanced phosphorylation of the myosin light chain and smooth muscle contraction (WO 2005/003101A2, WO 2005/034866A2).
Many compounds are known to have ROCK inhibition activity. Some of these compounds may not be easy to make and may require procedures that control their enantiomeric purities. There exists a need for simple and practical synthetic procedures to prepare ROCK inhibitor compounds of high chemical and enantiomeric purity.